TTD: The structurally related TTD module possess a characteristic β-barrel topology and comprise the Royal superfamily. The single Tudor domains of PHF1 and PHF19 have been shown to recognize H3K36me3, whereas the canonical TTD of 53BP1 associates with H4K20me2, and the hybrid TTD of JMJD2A binds H3K4me3 and H4K20me3. (1)